Projectile Roll Angle Measurement System Based On Semi-active Laser

In recent years,the semi-active laster terminal correction projectile has been the research hotspot with the characteristics of high precision,simple structure,strong anti-interference ability with other guidance,etc.Precise measurement method of projectile rolling angle is a key technology of the semi-active laser terminal.Considering intelligent ammunition for low cost,high overload and all-weather adaptability,some problems of projectile rolling angle measurement method still need to be solved.Therefore,this paper focues on the contents of the measurement of roll angle of the semi-active laster terminal correction projectile based on PSD.The main contents are as follows:The frame of measuring system of projectile roll angle based on PSD is established;The characteristics of the strapdown guidance system are analyzed based on PSD in detail,and the overall frame of the roll angle measurement system based on FPGA+DSP is designed.The system can achieve the fast extraction for the echo signal of narrow pulse width and low repetition rate,with a large dynamic range and high precision features.Based on the semi-active laser detection model,a solution model and error model of roll angle based on PSD are established,which lays a technical foundation for accurate extraction of projectile of the roll angle.The extraction circuit is designed based on the weak echo signal of narrow pulse width and low repetition rate.In order to capture the target in time,the extraction of the weak echo signal is especially important.Based on this analysis,the main factors affecting the SNR of the system are analyzed,the relationship between the SNR of system and roll angle error is determined.Moreover,to achieve the noise optimization design of the overall system,the system noise model including the PSD sensor,the first stage amplifier and the AGC circuit is established.According to the principle of the PSD roll angle calculation,an approach of ahead of the peak point detection based on the dual-comparator is proposed.This method obtains the peak point accurately while acquiring the peak point of narrow-pulse echo signal accurately.In order to get the velocity and projectile and meet the wide range of changes in the energy of the echo,a three-stage AGC circuit and its control strategy are designed.This method can accurately acquire the peak point of the narrow pulse width echo signal and the peak point time at the same time,which lays the foundation for obtaining the roll angle speed and the position of projectile.In addition,a three-level AGC circuit and its control strategy are designed to adapt to the wide variation of echo energy.Digital signal processing system of FPGA with DSP is designed.Based on the minimum system of FPGA and DSP,the functions of ADC acquisition,RS232 and flash storage are realized by using FPGA state machine and DSP.The extraction algorithm of PSD position coordinates,the extraction algorithm of the projectile roll angle speed and the extraction algorithm of the roll angle of the projectile are designed and realized.In addition,the data display PC is completed.The roll angle testing system based on PSD has been researched experimentally.Based on the two-dimensional PSD nonlinear correction system,the Newton interpolation algorithm is used to correct the roll angle measurement system proposed in this paper.The positioning error is 0.068 mm by this system.The ground semi-physical simulation platform is set up for the semi-active laser projectile,and the two aspects of spot location accuracy and roll angle solution error are independent evaluated for system.The experimental results shows that the error of spot location is 0.059 mm and the range of error of roll angle is ±3.5°,which satisfies the requirements of the error of roll angle in the guidance process.